We will continue our studies on host-coccidia relationships by observing chronic pathogenicity in the host after inoculation with Eimeria spp. utilizing histochemical techniques along with light and electron microscopy. We will also study the process of penetration by scanning electron microscopy. We will continue studies on the process of fertilization in the coccidia by inhibition of macrogametogenesis with chemosterilants and by introduction of microgametes into cell cultures following chemical treatment. We will continue studying the asexual development of first and second-generation merozoites in schizonts of certain coccidia in the host and in cultured cells. We will continue studies in progress on certain aspects of the immune response to coccidia including the effects of homologous antiserum on various developmental stages. Such studies will include culture of macrophages and transfer of lymphoid tissue from immune to non-immune recipient animals followed by challenge with coccidia. BIBLIOGRAPHIC REFERENCES: Kelly, G.L. and Youssef, N.N. 1975. Development of Eimeria vermiformis from Mice in Cultured Cells.